From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49691) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dxDKc-000351-Mk for qemu-devel@nongnu.org; Wed, 27 Sep 2017 10:29:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dxDKW-00032f-Oi for qemu-devel@nongnu.org; Wed, 27 Sep 2017 10:28:58 -0400 Received: from mx1.redhat.com ([209.132.183.28]:16703) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dxDKW-000325-FW for qemu-devel@nongnu.org; Wed, 27 Sep 2017 10:28:52 -0400 Date: Wed, 27 Sep 2017 15:28:38 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20170927142837.GB2108@work-vm> References: <20170926162058.30772-1-cohuck@redhat.com> <20170926162058.30772-2-cohuck@redhat.com> <338c8565-691e-a8bc-d8a6-3637ce13701d@redhat.com> <20170927114717.72bd69f8.cohuck@redhat.com> <20170927125606.65dc514d.cohuck@redhat.com> <14df9ad6-f0e9-cd51-04dd-4fe994808433@de.ibm.com> <4681e677-9e5a-4c1c-8e22-dc5c51b7286d@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <4681e677-9e5a-4c1c-8e22-dc5c51b7286d@redhat.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH 1/1] s390x: create a compat s390 phb for <=2.10 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Hildenbrand Cc: Christian Borntraeger , Cornelia Huck , Yi Min Zhao , qemu-devel@nongnu.org, agraf@suse.de, pasic@linux.vnet.ibm.com, jjherne@linux.vnet.ibm.com * David Hildenbrand (david@redhat.com) wrote: > On 27.09.2017 12:59, Christian Borntraeger wrote: > >=20 > >=20 > > On 09/27/2017 12:56 PM, Cornelia Huck wrote: > >> On Wed, 27 Sep 2017 18:25:00 +0800 > >> Yi Min Zhao wrote: > >> > >>> =E5=9C=A8 2017/9/27 =E4=B8=8B=E5=8D=885:47, Cornelia Huck =E5=86=99= =E9=81=93: > >>>> On Tue, 26 Sep 2017 20:40:25 +0200 > >>>> David Hildenbrand wrote: > >> > >>>>> I'd really really really (did I mention really?) favor something = like a > >>>>> dummy device, because we could easily handle the !CONFIG_PCI case= then. > >>>>> > >>>>> All these compat options and conditions will kill us someday... w= e're > >>>>> already patching around that whole stuff way too much. > >>>>> > >>>>> If we ever unconditionally created a device, we should keep doing= so. =20 > >>>> Yes, that whole thing is horrible, especially interaction with com= pat > >>>> machines. > >>>> > >>>> Do you have an idea on how to create such a dummy device (without > >>>> having to effectively copy a lot of configured-out code)? > >>>> > >>>> =20 > >>> How about in s390_pcihost_hot_plug() we check s390_has_feat(zpci)? > >>> If no zpci feature, we avoid plugging any pci device. > >>> Then we could always create phb. > >>> I think pcibus's vmstate is only data to migrate. > >> > >> That's still problematic if CONFIG_PCI is off. I currently don't hav= e a > >> better idea than either disallowing compat machines on builds withou= t > >> pci, or using a dummy device... > >=20 > > For this particular case your initial patch might be less problematic= than > > a dummy device, because the code that does the migration is NOT conta= ined > > in s390 specific code but in common PCI code instead. We would need t= o keep > > the dummy device always in a way that it will work with the common PC= I > > code. > >=20 >=20 > Interesting, so how is migration then handled for e.g. x86 or other > architectures that can work without CONFIG_PCI? I assume their migratio= n > should also break? It's tied to machine-type; the x86 i440fx and q35 machine types have PCI; you can't disable PCI while still having those machine types. (I don't know if you can disable PCI at all on x86) Dave > --=20 >=20 > Thanks, >=20 > David -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK